There are many different infant nutritional formulas that are commercially available or otherwise known in the infant formula art. These infant formulas comprise a range of nutrients to meet the nutritional needs of the growing infant, and typically include lipids, carbohydrates, protein, vitamins, minerals, and other nutrients helpful for optimal infant growth and development.
Most of these nutritional infant formulas are designed to assimilate or duplicate the composition and function of human milk. It is generally recognized, however, that human milk is preferred over synthetic infant formulas for the feeding of infants. It is also known that human milk provides improved immunological benefits to the breastfed infant, as well as long-term benefits in the area of certain cognitive developments.
It is also well known that the composition of human milk changes over the first few weeks following delivery of an infant. Human milk is referred to as colostrum during the first 5 days after birth, transition milk during days 6-14 after birth, and mature milk thereafter, and during each stage of lactation, the corresponding human milk composition differs considerably. Colostrum and transition milk, for example, have lower caloric densities than mature milk, as well as higher protein and lower carbohydrate concentrations. Vitamin and mineral concentrations also vary in the three defined human milk groups.
Most commercial infant formulas are similar in composition, although not identical, to mature human milk, and are used in both newborns as well as older infants. It is generally believed that the nutrient composition and higher energy content of mature milk, and thus the nutrient composition and higher energy content of most commercial infant formulas, benefit newborn infants given the rapid growth rate of infants during the initial weeks of life. In short, it has heretofore been accepted that the feeding of newborn infants should be conducted with an emphasis on encouraging infant growth, and that such growth is best accomplished via the feeding with commercial infant formulas having a similar nutrient and energy content to mature human milk.
However, more than 100 years ago, critical windows in development were first described in relation to imprinting in chicks. That nutrition can act during such windows to affect later biology was shown in the 1960s by McCance who found that rats raised in small litters, and therefore overfed postnatally, were larger in adulthood. Subsequently, early overfeeding in rats was shown to raise later concentrations of plasma insulin and cholesterol, while early nutrition in baboons permanently affected later risk of obesity and atherosclerosis. To provide research focus for such long-term effects, Lucas proposed the term “programming” and initiated experimental studies to test this concept in man, see Lucas A., Programming by early nutrition in man: in: Bock G R, Whelan J Eds. The childhood environment and adult disease. (CIBA Foundation Symposium 156). Whiley, Chichester, UK. 1991: 38-55.
Atul Singhal et al., Early nutrition in preterm infants and later blood pressure: two cohorts after randomised trials, The Lancet, Vol. 357, Feb. 10, 2001 at p. 413 (the disclosure of which is incorporated herein by reference) explain that the potential effect of early nutrition on cardiovascular disease is an issue of major public-health importance. Associations between low weight and thinness at birth and hypertension and coronary-artery disease in later life were thought to be consistent with the hypothesis that avoidance of over-nutrition in early life ‘programmes’ later cardiovascular outcomes such as blood pressure. The authors had an opportunity to test the hypothesis that feeding of breastmilk to premature infants programmes later blood pressure in a formal experimental intervention trial. In the early 1980s, human-milk banks were in common use to provide preterm infants with breastmilk from unrelated donors. Random assignment of preterm infants to donated human milk or formula was ethical because at that time the optimum diet for babies born preterm was uncertain and the long-term outcomes of early feeding regimens unknown. The reported study started in 1982. It consisted of two parallel randomised trials: one compared banked breastmilk with nutrient-enriched preterm formula; the other compared a standard term formula with the nutrient-enriched preterm formula. Planned follow-up allowed the authors to test the generic hypothesis that early nutrition influences later blood pressure and the a-priori specific hypothesis that consumption of human milk in infancy leads to lower blood pressure in later life.
Preterm formula, compared with standard formula, was enriched in protein and fat (2.0 g protein and 4.9 g fat per 100 mL compared with 1.5 g protein and 3.8 g fat per 100 mL) but not in carbohydrate (7.0 g per 100 mL in both). For infants fed maternal milk, intakes of protein and energy were estimated from 4935 complete 24 h collections of milk (about 1.5 g protein, 3.0 g fat, and 7.0 g carbohydrate per 100 mL), and nutrient values for donated banked breastmilk were measured in more than 600 samples of pooled banked breastmilk and the averages calculated (about 1.1 g protein, 2.0 g fat, and 7.0 g carbohydrate per 100 mL). The sodium concentration was 19.6 mmol/L in preterm formula, 11.0 mmol/L in expressed breastmilk, 8.3 mmol/L in term formula, and 7.2 mmol/L in banked breastmilk. Preterm formula was designed overall to meet what were then understood to be the special nutrient needs of the preterm infant.
As expected, early weight gain was significantly greater in infants assigned nutrient-enriched preterm formula than in those assigned banked breastmilk. Among the children followed up at age 13-16 years, there were no significant differences in systolic or diastolic blood pressure between the randomised groups in trials 1 and 2 at age 7.5-8.0 years. At age 13-16 years, mean arterial pressure was significantly lower in children assigned banked breastmilk than in those assigned preterm formula, mean difference 4.1 mm Hg. Diastolic blood pressure was 3.2 mm Hg lower in infants assigned banked breastmilk than in those assigned a preterm formula, a benefit similar to the 2.3 mm Hg difference in diastolic and 3.5 mm Hg difference in systolic blood pressure observed previously in the non-randomised study of children born at term. A decrease of about 3 mm Hg in diastolic blood pressure, estimated from the authors' and previous epidemiological studies, could have substantial public-health implications. For instance, analysis of randomised trials and the Framingham study suggests that a lowering of population-wide diastolic blood pressure in adults by only 2 mm Hg would reduce the prevalence of hypertension by 17%, the risk of coronary heart disease by 6%, and the risk of stroke and transient ischaemic attacks by 15%. Addition of such an intervention to existing hypertension treatment could therefore prevent an estimated 67000 (6%) events of coronary heart disease and 34 000 (13%) of stroke or transient ischaemic attack, each year, among the 35-64 age-group, in the USA alone. Furthermore, a mean reduction in blood pressure of 3 mm Hg underestimates the degree of lowering and benefit to children at the extremes of the distribution for blood-pressure change and, because blood pressure tracks from childhood into adult life with amplification of early differences, the blood-pressure difference between breastfed and nonbreastfed populations is likely to be substantially greater in adulthood.
In the UK, donor breastmilk (provided by unrelated donors to a milk bank) was generally the low-fat foremilk that dripped from the contralateral breast during breastfeeding of the donor's own baby. The authors considered the possibility that the lower fat and therefore energy content of such donor breastmilk, rather than any unique property of human milk itself, accounted for their findings but concluded that this possibility was unlikely and that non-nutritive factors in breastmilk or dietary factors in breastmilk rather than the formulas used were responsible for the results observed.
A further study by Singhal et al., Early nutrition and leptin concentrations in later life, Am J Clin Nutr 2002; 75:993-9 (the disclosure of which is incorporated herein by reference) also involved preterm infants who participated in two trials. In trial 1 subjects received either a nutrient-enriched preterm formula (Farley's Osterprem; Farley Health Products (a division of H J Heinz Company Ltd, Stockley Park, Uxbridge, United Kingdom) or breast milk donated by unrelated lactating women, and in trial 2 subjects received either the same preterm formula or a standard term formula (Farley's Ostermilk; Crookes Health Care). The assigned diets were given until the infants weighed 2000 g or were discharged to their homes. Compared with the standard formula (15 g protein/L and 38 g fat/L), the preterm formula was enriched in protein and fat (20 g protein/L and 49 g fat/L) but not carbohydrate (70 g/L in both formulas). For infants fed banked donated milk, protein and energy intakes were estimated from 600 donor milk pools collected from multiple donors (˜11 g protein, 20 g fat, and 70 g carbohydrate/L). The composition of the mothers' own expressed milk was measured in 4935 complete 24-h collections (˜15 g protein, 30 g fat, and 70 g carbohydrate/L). The leptin concentration relative to fat mass was 30% greater in the children who received a preterm formula at birth than in those who received one of the two standard diets. This difference was independent of population differences at birth or in adolescence, and given the experimental design, strongly supported an influence of early diet on later leptin concentrations. The authors therefore concluded that infancy, at least in preterm infants, could be a critical window for programming later leptin physiology and by inference the risk of obesity. The authors averred that the novelty of their study lay in its experimental design, in which infants were randomly assigned at birth to receive diets with different nutrient compositions. Thus, controlling for possible confounding factors, they found that dietary manipulation for an average of only one month markedly influenced leptin concentrations relative to fat mass up to 16 years later. These differences were seen in a combined comparison between the nutrient-enriched and standard diets, in a comparison between the preterm formula and the term formula (trial 2), and in a comparison between the preterm formula and banked donated breast milk (trial 1), although the difference in the latter comparison was not significant. Their further observational analysis that showed an association between consumption of human milk (maternal plus banked breast milk) and lower leptin concentrations relative to fat mass was consistent with the hypothesis that leptin concentrations are programmable by early diet. It should be noted, however, that the “dietary manipulation” contemplated by the authors was randomly assigning infants to one diet or the other, but nothing beyond that.
A secondary analysis by Stettler et al., Circulation, 2005; 111:1897-1903 of a cohort study of healthy infants born between 1965 and 1978 in the region of Iowa City, Iowa, USA concluded that in formula fed infants weight gain during the first week of life may be a critical determinant for the development of obesity several decades later. Although there is a throw-away suggestion that the results might suggest new approaches to obesity prevention, no specific consideration is given to any such approach and there is no data to suggest that weight gain in the critical period can be controlled effectively to reduce or prevent long term obesity which may become apparent decades later. Moreover there is no disclosure or suggestion that changing the composition of modern formulas could be beneficial to long-term obesity risk i.e. risk of obesity from 6 months onwards and/or in childhood or adulthood. That this link was not made by the authors is further emphasized by their statement in the discussion that compared with breastfeeding, formula feeding has been associated with more rapid absolute weight gain in early infancy and with obesity in adolescence, but because their study was limited to exclusively formula-fed subjects, their finding cannot be explained by infant feeding mode. Therefore no link had been made between mode of early feeding and later obesity.
WO 2008/071667 (Haschke et al., Nestec S. A.) discloses a formula for infants at risk of developing obesity later in life which comprises a protein source, a lipid source and a carbohydrate source and has a protein content of less than 1.8 g/100 kcal and an energy density of less than 650 kcal/liter. In an embodiment the formula comprises 63 kcal/liter and 0.945 g/liter protein. The formula is intended for feeding to infants born to overweight or obese mothers from the age of three months and subsequently as part of a mixed diet during the introduction of solid foods until weaning is complete at the age of 12 months. No mention is made of the benefits of avoiding over-nutrition in the period immediately after birth e.g. in the two weeks after birth when the mother would be providing colostrum and transition milk and of the advantages flowing from avoidance of over-nutrition during that period.